By Alecia Reid

UPPER DARBY, Pa. (CBS) — We are learning more about the timeline of events leading up to the death of 21-year-old Dianna Brice. Her body was found in a wooded lot in Southwest Philadelphia nearly a week after she disappeared.

The investigation into what happened to Brice is heating up. Detectives are following every lead in hopes one of them will help them close in on the person responsible for her murder.

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Gathering bags of evidence, Philadelphia Crime Scene Investigators spent a significant amount of time at the Upper Darby Police Department on Tuesday. It was another step in the homicide investigation.

They are officially looking at two vehicles. Justin Smith’s torched 2018 black Ford Fusion and now a rental car that investigators believe may have been involved in the dumping of Brice’s body.

A source close to the investigation tells Eyewitness News the 21-year-old pregnant mother was shot multiple times.

The timeline of events shows, last Tuesday around 11:30 a.m., Smith, Brice’s boyfriend, picked her up from K Laundry in Lansdowne. Before she was picked up, her mother noticed she was visibly upset but wouldn’t say why.

By 1:30 p.m. the victim’s mom calls to say the laundry is done and it’s time to head home. Brice says she never made it to the pharmacy to pick up her prescription but would meet at home.

That was the last time Brice was in contact with anyone. Frantic to get in touch, Betty Cellini, Brice’s mother, calls Smith. He claims they got into an argument and Brice left.

A threat to file a police report angers Smith and his phone then goes unanswered.

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By 5:30 p.m. Smith’s car is spotted abandoned and on fire at 59th and Florence Streets in Southwest Philadelphia.

A little over a mile from where Brice’s body was found a week later.

“It’s just tragic. It speaks to the senseless violence that occurs every day out there,” Upper Darby Police Superintendent Timothy Bernhardt said. “And here’s a mother of a 4-year-old child and was expecting her second child, she was four months pregnant, and that child will never see his mother again and her family will never see her daughter again. It’s tragic.”

A source tells Eyewitness News there may be a third person involved in the case.

Eyewitness News is awaiting confirmation from the police.

Smith remains a person of interest. Eyewitness News spoke with his father Wednesday. He says everyone’s stomach is in knots. They have no idea what is going on.

The family has not heard from his son and right now, they are letting detectives do their work.

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A GoFundMe page has been in an effort to cover Brice’s funeral cost and to start a college fund for her son.